Polychlorinated biphenyls , synthesis

Miranda, C.L., M.C. Henderson, J.L. Wang, H.S. Nakaue, and D.R. Buhler. 1987. Effects of polychlorinated biphenyls on porphyrin synthesis and cytochrome P-450-dependent monooxygenases in small intestine and liver of Japanese quail. Jour. Toxicol. Environ. Health 20 27-35. 

Environmental chemicals and pollutants are also capable of inducing P450 enzymes. As previously noted, exposure to benzo[a]pyrene and other polycyclic aromatic hydrocarbons, which are present in tobacco smoke, charcoal-broiled meat, and other organic pyrolysis products, is known to induce CYP1A enzymes and to alter the rates of drug metabolism. Other environmental chemicals known to induce specific P450s include the polychlorinated biphenyls (PCBs), which were once used widely in industry as insulating materials and plasticizers, and 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin, TCDD), a trace byproduct of the chemical synthesis of the defoliant 2,4,5-T (see Chapter 56). 

Figure 16.3 gives the structural formulas of some of the more important aryl halides. These compounds are made by the substitution chlorination of aromatic hydrocarbons, as shown, for example, by the reaction below for the synthesis of a polychlorinated biphenyl ... 

Polychlorinated Biphenyls (PCBs). The PCBs were observed in the stack effluents during the combustion of coal but these compounds were not produced in the combustion process by a de novo synthesis or from precursor compounds. The source of the PCBs was the indoor air used to support the combustion. This indoor air contained 0.11 ug/M3 of PCBs the concentration of PCBs in the stack gas was only 0.02 yg/M3 when coal containing no detectable level of PCBs was burned. For perspective, this emission level should be compared to the average ambient outdoor air level of about 0.006 yg/M3. 

Groce DF, Alley CC, Patterson DG (1989), Chemosphere 19 225-232.. .Synthesis of tetrachlo-ro-, pentachloro-, and hexachlorodibenzofurans from the pyrolysis of polychlorinated biphenyls"... 

Choksi NY, Kodavanti PR, Tilson HA, et al. 1997. Effects of polychlorinated biphenyls (PCBs) on brain tyrosine hydroxylase activity and dopamine synthesis in rats. Fundam Appl Toxicol 39(l) 76-80. 

Exon JH, Talcott PA, Koller LD. 1985. Effect of lead, polychlorinated biphenyls, and cyclophosphamide on rat natural killer cells, interleukin 2, and antibody synthesis. Fundam Appl Toxicol 5 158-164. 

Haraguchi, K., H. Kuroki, and Y. Masuda. 1987. Synthesis and characterization of tissue-retainable methylsulfonyl polychlorinated biphenyl isomers. J. Agric. Food Chem. 35 178-182. 

MAJOR USES Intermediate for polychlorinated biphenyls organic synthesis heat transfer agent plant disease control dyeing assistant for polyesters manufacturing of benzidine fun-gistat in packaging of citrus fruit. 

OTHER COMMENTS used as a heat transfer agent used as a fungistat for oranges (applied to inside of shipping container) used in organic synthesis used as an intermediate for polychlorinated biphenyls and in the manufacture of benzindine. 

PCBs and PCDDs. In Diarylide Yellow manufacture, the use of formate buffer to enhance pigment transparency for offset ink was discontinued in the nineteen seventies, when it was realized that polychlorinated biphenyls were being produced as an undesirable by-product of the coupling reaction. In Phthalocyanine Blue crude synthesis, the commonly used solvent, trichlorobenzene, was also discontinued in the US, as a potential source of poly-chlorinated biphenyls. More recently, use of chloranil, manufactured from chlorinated phenols, has been discontinued in the synthesis of dioxazine violet crude and sulfonated dioxazine acid dyes, so as to minimize by-product formation of polychlorinated dibenzodioxins and dibenzofurans (PCDDs/PCDFs). A new grade ofhigh purity chloranil is now produced from hydroquinone for dye and pigment manufacture. 

Endocrine disrupting compounds = Exogenous agents that interfere with the synthesis, secretion, transport, binding, action, or elimination of natural hormones in the body that are responsible for the maintenance of homeostasis, reproduction, development, and/or behavior (e.g., alkylphenols, alkylphenol polyethoxylates, polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), phthalates, bisphenol-A, polybrominated flame retardants, dioxins, furans, herbicides, pesticides, and steroid hormones). 

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